Tag Archives: transparency

Why are some inks more opaque than others?

Why are some printmaking inks more opaque than others? I’m currently working on a commission that won’t be unveiled until after it is delivered to its new collector. Without giving away the details, I found myself needing to shift from a middle blue tone into much darker greens. Enter the yellow opaque ink…

Gamblin’s Relief Ink Hansa Yellow Light is quite opaque.

Opacity vs transparency : not all inks are the same

After using Gamblin’s relief inks for a while, I intuitively know that yellow, napthol scarlet and titanium white will be the most opaque. Other inks like quinacridone red and phthalo blue will be very transparent. For me opacity means that it will cover up the color underneath more completely, and combine with it less. Even with opaque ink straight from the can, you will never get the color on the paper that you see on the glass. They aren’t completely opaque.

I wanted to answer the question of why some inks were more opaque than others. It was remarkably difficult to get such an explanation without jumping off into a discussion of physics for which I was not qualified.

Getting to the why of opacity and transparency

Mixing in some transparent blue didn’t make my yellow much less opaque.

Two on-line sources got me closer to an explanation of why inks vary in opacity. Why Some Paints are Transparent and Others Opaque, a page from Natural Pigments on-line store, has the most complete explanation. The Anatomy of Paint: Pigment and Binder from Essential Vermeer 2.0 has a discussion with a bit less physics.

The answer has three variables

Relative Refractive Indicies

Remember that all pigments whether naturally gathered or industrially created all start out as a powder. The powder is combined with a binder to allow the pigment to be applied to a surface. With printmaking, burnt plate oil (a heated version of linseed oil) is the binder.

Both pigments and binders have a rating for their ability to refract — or scatter — light. The more similar the number, the more likely the created ink will be transparent — or not scattering the light. Linseed oil has an index of 1.479 so pigments that have a very similar index will allow the most light to pass through, appearing transparent. Other pigments like zinc oxide, have an index of 2.00, and therefore appear opaque — not allowing any of the light through.

Particle Size

In my previous post on gold ink, I noted that my favorite one — Charbonnel’s Etching Ink Gold — had almost noticeable particles. It is very opaque, and this makes sense because the light is being refracted off the (larger) gold pigment particles, and can’t make its way down through the ink layers to the white paper.

Imagine all of those light particles struggling to make it through to the white paper!

Distribution of Pigment

This variable is obvious to me, as I liberally mix transparent base into my relief inks to increase the transparency of any color. Even still, I can never achieve the transparency of a phthalo blue with the yellow or white inks. This is probably because of the above two variables.

You can see that this mixed ink is fairly opaque because I can’t see any of the support buttons that are beneath the glass on the table,

I’m not sure I completely understand refractive indicies, but I do get a kick out of imagining the light rays trying mightily to penetrate my layer of ink and make it to the white paper.

Now back to my commission and to some new work. Science class is concluded.

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I do not intend to be opaque

I started out my adult art study with watercolors, a most unforgiving medium. Watercolor requires immediate commitment with the knowledge that it is difficult to undo what has been done. Yes, there is white, but it is opaque, unlike most watercolors. I was taught not to rely on it to fix my mistakes.

I’ve carried my aversion to opaque white into my printmaking. For the first few years I used only inks thinned with transparent base, gradually building up my image. This had two consequences that I didn’t like. First, the initial layers were by necessity short on chroma. I rarely accomplished a brilliant yellow. Second, it made using a complementary or split complementary color scheme very difficult. No matter how much purple you put over yellow, you are always going to get some kind of brown.

But all that has changed. I’ve started using opaque ink in places where I want rich colors, and don’t need that brilliant transparency of the white paper shining through the inks.

water 2 layer

Two layers of transparent blue, including a rainbow roll provide the base of the linocut.

I chose this watery pattern from a close-up of the Mosel River in Germany. I knew I didn’t want the blues to get darker, and I needed to switch to a different series of colors. Enter opaque white. (more…)

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This is only a test

There are many interesting phenomena in nature, and we are treated to images of them everyday. Internet-shared imagery zooms in and out showing us the incredible complexity of our natural world, and I am often inspired. The problem comes when I want to translate that inspiration into a linocut. Sometimes a fascinating idea becomes unsuccessful in the studio.

Many of my ideas involve intricate carving and numerous layers of ink, so I like to do a test when I’m thinking about a new series of work. I used the idea of a sea fan for a demonstration at my recent Open Studios, and decided to further pursue this topic. To get a good idea of what things will look like, I had to use a block larger than the card-sized one used for the demo. Patterns need a bit of space to develop.

(more…)

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